T. Sakai, H. Yamada, S. Fukushima, and K. Ito Electronic Navigation Research Institute, Japan T. Sakai, H. Yamada, S. Fukushima, and K. Ito Electronic

T. Sakai, H. Yamada, S. Fukushima, and K. ItoElectronic Navigation Research Institute, Japan

T. Sakai, H. Yamada, S. Fukushima, and K. ItoElectronic Navigation Research Institute, Japan

Generation and Evaluation ofQZSS L1-SAIF Ephemeris Information

Generation and Evaluation ofQZSS L1-SAIF Ephemeris Information

ION GNSS 2011ION GNSS 2011Portland, ORPortland, OR

Sept. 20-23, 2011Sept. 20-23, 2011

ION GNSS 20-23 Sept. 2011 - ENRIION GNSS 20-23 Sept. 2011 - ENRI

SSLIDELIDE 22IntroductionIntroduction

• QZSS (Quasi-Zenith Satellite System) programQZSS (Quasi-Zenith Satellite System) program::– Regional navigation service broadcast from high-elevation angle by a combination Regional navigation service broadcast from high-elevation angle by a combination

of three satellites on the inclined geosynchronous (quasi-zenith) orbit;of three satellites on the inclined geosynchronous (quasi-zenith) orbit;– Broadcast GPS-like supplemental signals on three frequencies and two augmentatiBroadcast GPS-like supplemental signals on three frequencies and two augmentati

on signals, L1-SAIF and LEX;on signals, L1-SAIF and LEX;– The first QZS satellite was successfully launched on Sept. 11, 2010.The first QZS satellite was successfully launched on Sept. 11, 2010.

• L1-SAIF L1-SAIF (Submeter-class Augmentation with Integrity Function) signal offers(Submeter-class Augmentation with Integrity Function) signal offers::– Submeter accuracy wide-area differential correction service;Submeter accuracy wide-area differential correction service;– Integrity function for safety of mobile users; andIntegrity function for safety of mobile users; and– Ranging functionRanging function for position availability; all on L1 single frequency. for position availability; all on L1 single frequency.

• ENRI has been developing L1-SAIF signal and experimental facilityENRI has been developing L1-SAIF signal and experimental facility::– Signal design: SBAS-like message stream on L1 C/A (PRN 183);Signal design: SBAS-like message stream on L1 C/A (PRN 183);– Implemented L1-SAIF Master Station (L1SMS);Implemented L1-SAIF Master Station (L1SMS);– Need to broadcast ephemeris message to make ranging function available.Need to broadcast ephemeris message to make ranging function available.

What is the best way to generate ephemeris information for L1-SAIF?What is the best way to generate ephemeris information for L1-SAIF?


SSLIDELIDE 33QZSS ConceptQZSS Concept

• Broadcast signal from high elevation angle;Broadcast signal from high elevation angle;

• Applicable to navigation services for Applicable to navigation services for mountain area and urban canyon;mountain area and urban canyon;

• Augmentation signal from the zenith could Augmentation signal from the zenith could help users to acquire other GPS satellites at help users to acquire other GPS satellites at any time.any time.

• Footprint of QZSS orbit;Footprint of QZSS orbit;• Centered 135E;Centered 135E;• Eccentricity 0.075, Inclination 43deg.Eccentricity 0.075, Inclination 43deg.

QZSQZSGPS/GEOGPS/GEO


SSLIDELIDE 44Inclined Geosynchronous OrbitInclined Geosynchronous Orbit

Orbital Planes of QZSS (3 SVs)Ground Track

Perigee Perigee 32000km32000km

ApogeeApogee40000km40000km

• Semi-major axis (42164km) is equal to GEO orbit: synchronous with rotation of Semi-major axis (42164km) is equal to GEO orbit: synchronous with rotation of the earth;the earth;

• Inclined obit makes ground track ‘8’-figure; Called IGSO or Quasi-Zenith Orbit;Inclined obit makes ground track ‘8’-figure; Called IGSO or Quasi-Zenith Orbit;• With three or more satellites on the same ground track, navigation service can With three or more satellites on the same ground track, navigation service can

be provided from zenith to regional users at any time.be provided from zenith to regional users at any time.

8:408:40

15:2015:20


SSLIDELIDE 55

L-band Helical Array Antenna

L1-SAIF Antenna

Laser Reflector

C-band TTC Antenna

Radiation Cooled TWTTWSTFT Antenna

25.3m

Successfully launched on Sept. Successfully launched on Sept. 11, 2010 and settled on Quasi-11, 2010 and settled on Quasi-Zenith Orbit (IGSO).Zenith Orbit (IGSO).

Space Segment: QZS-1Space Segment: QZS-1

Mass4,020kg (wet) 1,802kg (dry) (NAV Payload： 320kg)

PowerApprox. 5.3 kW (EOL) (NAV Payload: Approx. 1.9kW)

Design Life 10 years


SSLIDELIDE 66QZSS Frequency PlanQZSS Frequency Plan

Find detail in IS-QZSS document.Find detail in IS-QZSS document.

SignalSignal ChannelChannel FrequencyFrequency BandwidthBandwidth Min. Rx PowerMin. Rx Power

QZS-L1CQZS-L1CL1CDL1CD

1575.42 MHz1575.42 MHz

24 MHz24 MHz ––163.0 dBW163.0 dBW

L1CPL1CP 24 MHz24 MHz – – 158.25 dBW158.25 dBW

QZS-L1-C/AQZS-L1-C/A 24 MHz24 MHz – – 158.5 dBW158.5 dBW

QZS-L1-SAIFQZS-L1-SAIF 24 MHz24 MHz – – 161.0 dBW161.0 dBW

QZS-L2CQZS-L2C 1227.6 MHz1227.6 MHz 24 MHz24 MHz – – 160.0 dBW160.0 dBW

QZS-L5QZS-L5L5IL5I

1176.45 MHz1176.45 MHz25 MHz25 MHz – – 157.9 dBW157.9 dBW

L5QL5Q 25 MHz25 MHz – – 157.9 dBW157.9 dBW

QZS-LEXQZS-LEX 1278.75 MHz1278.75 MHz 42 MHz42 MHz – – 155.7 dBW155.7 dBW

InteroperabilityInteroperability

GPS-like supplemental GPS-like supplemental signals with minimum signals with minimum modifications from GPS modifications from GPS signalssignals

SBAS-like augmentation SBAS-like augmentation signal (250bps)signal (250bps)

QZSS-specific augmenta-tiQZSS-specific augmenta-tion signal (2kbps)on signal (2kbps)

1575.42 MHz1575.42 MHz


SSLIDELIDE 77

• QZSS broadcasts wide-area augmentation signalQZSS broadcasts wide-area augmentation signal::– Called L1-SAIF (Submeter-class Augmentation with Integrity Function);Called L1-SAIF (Submeter-class Augmentation with Integrity Function);

– Designed and developed by ENRI.Designed and developed by ENRI.

• L1-SAIF signal offersL1-SAIF signal offers::– Wide-area differential correction service for improving position accuracy; TargeWide-area differential correction service for improving position accuracy; Targe

t accuracy: 1 meter for horizontal;t accuracy: 1 meter for horizontal;

– Integrity function for safety of mobile users; andIntegrity function for safety of mobile users; and

– Ranging functionRanging function for position availability. for position availability.

• Augmentation to GPS L1C/A based on SBASAugmentation to GPS L1C/A based on SBAS::– Broadcast on L1 freq. with RHCP; Common antenna and RF front-end;Broadcast on L1 freq. with RHCP; Common antenna and RF front-end;

Modulated by BPSK with C/A code (PRN 183);Modulated by BPSK with C/A code (PRN 183); 250 bps data rate with 1/2 FEC; message structure is identical with SBAS;250 bps data rate with 1/2 FEC; message structure is identical with SBAS; Differences: Large Doppler and additional messages.Differences: Large Doppler and additional messages.

– Specification of L1-SAIF: See IS-QZSS document (Available at JAXA HP).Specification of L1-SAIF: See IS-QZSS document (Available at JAXA HP).

QZSS L1-SAIF SignalQZSS L1-SAIF Signal


SSLIDELIDE 88L1-SAIF SignalL1-SAIF Signal

User GPSUser GPSReceiversReceivers

• Three functions by a single signal: ranging, error Three functions by a single signal: ranging, error correction (Target accuracy: 1m), and integrity;correction (Target accuracy: 1m), and integrity;

• User receivers can receive both GPS and L1-SAIF User receivers can receive both GPS and L1-SAIF signals with a single antenna and RF front-end;signals with a single antenna and RF front-end;

• Message-oriented information transmission: flexible Message-oriented information transmission: flexible contents.contents.

SAIFSAIF ：： Submeter-class Augmentation with Integrity FunctionSubmeter-class Augmentation with Integrity Function

RangingRangingFunctionFunction

ErrorErrorCorrectionCorrection

IntegrityIntegrityFunctionFunction

QZS satelliteQZS satellite

GPS ConstellationGPS Constellation

Ranging SignalRanging Signal


SSLIDELIDE 99L1-SAIF Message StructureL1-SAIF Message Structure

PreamblePreamble8 bits8 bits

Message TypeMessage Type6 bits6 bits

Data FieldData Field212 bits212 bits

CRC parityCRC parity24 bits24 bits

1 message = 250 bits broadcast every second

MTMT

00

11

2 - 52 - 5

66

77

99

1010

1212

1717

1818

ContentsContents

Test modeTest mode

PRN maskPRN mask

Fast correction & UDREFast correction & UDRE

UDREUDRE

Degradation factor for FCDegradation factor for FC

GEO ephemerisGEO ephemeris

Degradation parameterDegradation parameter

SBAS time informationSBAS time information

GEO almanacGEO almanac

IGP maskIGP mask

IntervalInterval[s][s]

66

120120

6060

66

120120

120120

120120

300300

300300

300300

2424

2525

2626

2727

2828

6363

FC & LTCFC & LTC

Long-term correctionLong-term correction

Ionospheric delay & GIVEIonospheric delay & GIVE

SBAS service messageSBAS service message

Clock-ephemeris covarianceClock-ephemeris covariance

Null messageNull message

66

120120

300300

300300

120120

——

MTMT ContentsContents IntervalInterval[s][s]

Transmitted FirstTransmitted First


SSLIDELIDE 1010L1-SAIF Message (1)L1-SAIF Message (1)

Message TypeMessage Type ContentsContents Used byUsed by StatusStatus

00 Test modeTest mode SBAS and L1-SAIFSBAS and L1-SAIF FixedFixed

11 PRN maskPRN mask FixedFixed

2 to 52 to 5 Fast correction & UDREFast correction & UDRE FixedFixed

66 UDREUDRE FixedFixed

77 Degradation factor for FCDegradation factor for FC FixedFixed

1010 Degradation parameterDegradation parameter FixedFixed

1818 IGP maskIGP mask FixedFixed

2424 Mixed fast/long-term correctionMixed fast/long-term correction FixedFixed

2525 Long-term correctionLong-term correction FixedFixed

2626 Ionospheric delay & GIVEIonospheric delay & GIVE FixedFixed

99 GEO ephemerisGEO ephemeris SBASSBAS FixedFixed

1717 GEO almanacGEO almanac SBASSBAS FixedFixed

1212 SBAS network timeSBAS network time SBASSBAS FixedFixed

88 ReservedReserved SBASSBAS FixedFixed

SBAS and L1-SAIFSBAS and L1-SAIF










SSLIDELIDE 1111L1-SAIF Message (2)L1-SAIF Message (2)

Message TypeMessage Type ContentsContents Used byUsed by StatusStatus

2727 SBAS service messageSBAS service message SBASSBAS FixedFixed

29 to 5129 to 51 UndefinedUndefined —— ——

2828 Clock-ephemeris covarianceClock-ephemeris covariance SBAS and L1-SAIFSBAS and L1-SAIF FixedFixed

6262 ReservedReserved SBAS and L1-SAIFSBAS and L1-SAIF FixedFixed

6363 Null messageNull message SBAS and L1-SAIFSBAS and L1-SAIF FixedFixed

5252 TGP maskTGP mask L1-SAIFL1-SAIF TentativeTentative

5656 Intersignal biasesIntersignal biases L1-SAIFL1-SAIF TentativeTentative

5757 Ephemeris-related parameterEphemeris-related parameter L1-SAIFL1-SAIF TBDTBD

5858 QZS ephemerisQZS ephemeris L1-SAIFL1-SAIF TentativeTentative

5959 QZS almanacQZS almanac L1-SAIFL1-SAIF TBDTBD

6060 Regional informationRegional information L1-SAIFL1-SAIF TBDTBD

6161 ReservedReserved L1-SAIFL1-SAIF TentativeTentative

5353 Tropospheric delayTropospheric delay L1-SAIFL1-SAIF TentativeTentative

54 to 5554 to 55 Advanced Ionospheric delayAdvanced Ionospheric delay L1-SAIFL1-SAIF TBDTBD


SSLIDELIDE 1212Example Position ErrorExample Position Error

• Example of user position error at Site 94Example of user position error at Site 940058 (Takayama: near center of monitor 0058 (Takayama: near center of monitor station network);station network);

• Realtime operation with MSAS-like 6 moRealtime operation with MSAS-like 6 monitor stations;nitor stations;

• Period: 19-23 Jan. 2008 (5 days).Period: 19-23 Jan. 2008 (5 days).

HorizontalHorizontalErrorError

VerticalVerticalErrorError

1.45 m1.45 m 2.92 m2.92 m

6.02 m6.02 m 8.45 m8.45 m

SystemSystem

StandaloneStandaloneGPSGPS

0.29 m0.29 m 0.39 m0.39 m

1.56 m1.56 m 2.57 m2.57 mL1-SAIFL1-SAIF

RMSRMS

MaxMax

RMSRMS

MaxMax

Note: Results shown here were obtained with survey-Note: Results shown here were obtained with survey-grade antenna and receivers in open sky condition.grade antenna and receivers in open sky condition.

Standalone GPSStandalone GPSAugmented by L1-SAIFAugmented by L1-SAIF


SSLIDELIDE 1313Broadcast Ephemeris for RangingBroadcast Ephemeris for Ranging

• Orbit Information for ranging function:Orbit Information for ranging function:– Need to broadcast ephemeris information (navigation-grade orbit information) oNeed to broadcast ephemeris information (navigation-grade orbit information) o

n QZS signal in order to use it for ranging;n QZS signal in order to use it for ranging;– QZS L1C/A, L2C, L5, and L1C broadcast ephemeris information on their navigQZS L1C/A, L2C, L5, and L1C broadcast ephemeris information on their navig

ation message similar with GPS; Available since June 2011;ation message similar with GPS; Available since June 2011;– How about L1-SAIF and LEX signals?How about L1-SAIF and LEX signals?

• Option A: Do not broadcast on L1-SAIF, but on other signals:Option A: Do not broadcast on L1-SAIF, but on other signals:– L1-SAIF users receive and utilize ephemeris information broadcast on L1C/A, LL1-SAIF users receive and utilize ephemeris information broadcast on L1C/A, L

2C, L5, or L1C signals;2C, L5, or L1C signals; Antenna offset may be cancelled by differential correction.Antenna offset may be cancelled by differential correction.

– Users must receive al least two signals (eg. L1-SAIF + L1C/A) to use ranging fUsers must receive al least two signals (eg. L1-SAIF + L1C/A) to use ranging function of L1-SAIF signal.unction of L1-SAIF signal.

• Option B: Broadcast ephemeris information on L1-SAIFOption B: Broadcast ephemeris information on L1-SAIF::– Users can use QZS for ranging by receiving only L1-SAIF signal;Users can use QZS for ranging by receiving only L1-SAIF signal;– Require to design some new message because SBAS GEO ephemeris messaRequire to design some new message because SBAS GEO ephemeris messa

ge is not applicable; MT58 needs to be designed.ge is not applicable; MT58 needs to be designed.

We employWe employthis optionthis option


SSLIDELIDE 1414Ephemeris Message DesignEphemeris Message Design

• Requirements for ephemeris information:Requirements for ephemeris information:– Contained by a single message (212 bits);Contained by a single message (212 bits);

GPS legacy-Nav message consumes 420 bits for a set of ephemeris information of a GPS legacy-Nav message consumes 420 bits for a set of ephemeris information of a single GPS SV;single GPS SV;

SBAS GEO ephemeris message consists of only 204 bits; But this is for GEO.SBAS GEO ephemeris message consists of only 204 bits; But this is for GEO.

– Available for 600-900 seconds from broadcast;Available for 600-900 seconds from broadcast;– SV position error should be within 0.3-0.5m;SV position error should be within 0.3-0.5m;

Will be cancelled by applying differential corrections;Will be cancelled by applying differential corrections; The minimum resolution of corrections is 0.125m.The minimum resolution of corrections is 0.125m.

– Clock correction term should cover a range of Clock correction term should cover a range of 1ms.1ms. Required by payload developer during discussion of specification.Required by payload developer during discussion of specification.

• Representations in other systems:Representations in other systems:– GPS legacy-Nav: Representation by Keplerian 6-element parameters;GPS legacy-Nav: Representation by Keplerian 6-element parameters;– GLONASS: Represented by position, velocity, and acceleration in ECEF;GLONASS: Represented by position, velocity, and acceleration in ECEF;

Users need numerical integration to obtain the position of the intended moment.Users need numerical integration to obtain the position of the intended moment.

– SBAS: Transmit position, velocity, and acceleration in ECEF.SBAS: Transmit position, velocity, and acceleration in ECEF. No need for numerical integration.No need for numerical integration.


SSLIDELIDE 1515GPS Ephemeris for MEOGPS Ephemeris for MEO

Item Bits Contents

toc 16 Epoch time

toe 16 Epoch time

af0 22 Clock corr. (const)

af1 16 Clock corr. (1st order)

af2 8 Clock corr. (2nd order)

M0 32 Mean anomaly

0 32 Longitude of ascension

32 Argument of perigee

i0 32 Inclination

n 16 Mean motion

Item Bits Contents

e 32 Eccentricity

32 Semi-major axis

24 Rate of

14 Rate of i

Crc 16 Harmonic correction

Crs 16 Harmonic correction

Cuc 16 Harmonic correction

Cus 16 Harmonic correction

Cic 16 Harmonic correction

Cis 16 Harmonic correction

Total 420 Stored in 3 SFs (18s)

AA

ii....


SSLIDELIDE 1616GLONASS Ephemeris for MEOGLONASS Ephemeris for MEO

Item Bits Range Resolution Contents

tb 7 15-1425 min 15 min Epoch time

n 22 2-9 s 2-30 s Clock correction (const)

n 11 2-30 s/s 2-40 s/s Clock correction (1st order)

x 27 27000 km 2-11 km Position X in ECEF

y 27 27000 km 2-11 km Position Y in ECEF

z 27 27000 km 2-11 km Position Z in ECEF

vx 24 4.3 km/s 2-20 km/s Velocity X in ECEF

vy 24 4.3 km/s 2-20 km/s Velocity Y in ECEF

vz 24 4.3 km/s 2-20 km/s Velocity Z in ECEF

5 6.2 m/s2 2-30 km/s2 Acceleration X in ECEF (only perturbation)

5 6.2 m/s2 2-30 km/s2 Acceleration Y in ECEF (only perturbation)

5 6.2 m/s2 2-30 km/s2 Acceleration Z in ECEF (only perturbation)

Total 208 Stored in 4 strings (8s)

xx

yy

zz

....

....

....


SSLIDELIDE 1717SBAS Ephemeris for GEOSBAS Ephemeris for GEOItem Bits Range Resolution Contents

t0,GEO 13 0-86384 s 16 s Epoch time

URA 4 0-15 1 Accuracy indicator

x 30 42950 km 0.08 m Position X in ECEF

y 30 42950 km 0.08 m Position Y in ECEF

z 25 6710 km 0.4 m Position Z in ECEF

dx/dt 17 40.96 m/s 0.625 mm/s Velocity X in ECEF

dy/dt 17 40.96 m/s 0.625 mm/s Velocity Y in ECEF

dz/dt 18 524.288 m/s 4 mm/s Velocity Z in ECEF

d2x/dt2 10 6.4 mm/s2 12.5 m/s2 Acceleration X in ECEF

d2y/dt2 10 6.4 mm/s2 12.5 m/s2 Acceleration Y in ECEF

d2z/dt2 10 32 mm/s2 62.5 m/s2 Acceleration Z in ECEF

aGf0 12 0.9537 s 2-31 s Clock correction (const)

aGf1 8 0.11642 ns/s 2-40 s/s Clock correction (1st order)

Total 204 Stored in 1 msg (1s)


SSLIDELIDE 1818QZSS SV Position in ECEFQZSS SV Position in ECEF

• Computed based on broadcast ephemeris on QZSS L1C/A for day of Computed based on broadcast ephemeris on QZSS L1C/A for day of 2011-08-18;2011-08-18;

• QZS-1 was operating normally and healthy except LEX signal.QZS-1 was operating normally and healthy except LEX signal.

QZS-1QZS-1Broadcast Nav MsgBroadcast Nav Msgon L1C/A PRN 193on L1C/A PRN 193

2011-08-182011-08-1800:00 to 24:00 GPST00:00 to 24:00 GPST

GPS/QZSS RxGPS/QZSS Rx @Koganei, Tokyo@Koganei, Tokyo

Processing by ENRIProcessing by ENRI

24 different IODEs24 different IODEsin 2846 framesin 2846 frames


SSLIDELIDE 1919QZSS SV Velocity in ECEFQZSS SV Velocity in ECEF


2011-08-182011-08-1800:00 to 24:00 GPST00:00 to 24:00 GPST




• Velocity of QZS-1 computed from broadcast ephemeris.Velocity of QZS-1 computed from broadcast ephemeris.


SSLIDELIDE 2020QZSS SV Acceleration in ECEFQZSS SV Acceleration in ECEF

• Acceleration of QZS-1 computed from broadcast ephemeris.Acceleration of QZS-1 computed from broadcast ephemeris.


2011-08-182011-08-1800:00 to 24:00 GPST00:00 to 24:00 GPST





SSLIDELIDE 2121Representation of AccelerationRepresentation of Acceleration

• Reduction of information:Reduction of information:– GLONASS transmits ephemeris information as position, velocity, and acceleratiGLONASS transmits ephemeris information as position, velocity, and accelerati

on in ECEF;on in ECEF; Navigation-grade ephemeris is provided in 208 bits for a single GLONASS SV;Navigation-grade ephemeris is provided in 208 bits for a single GLONASS SV; Broadcast information is valid for 15 minutes; Enough for L1-SAIF;Broadcast information is valid for 15 minutes; Enough for L1-SAIF;

– Centripental acceleration is removed from transmitted information;Centripental acceleration is removed from transmitted information; These terms can be computed for the specific position and velocity of SV;These terms can be computed for the specific position and velocity of SV; GLONASS ICD A.3.1.2 gives the equations below (with some corrections).GLONASS ICD A.3.1.2 gives the equations below (with some corrections).

– This technique is applicable to L1-SAIF ephemeris representation.This technique is applicable to L1-SAIF ephemeris representation.

Transmit theseTransmit theseperturbation termsperturbation terms


SSLIDELIDE 2222Perturbation TermPerturbation Term

• Acceleration of QZS-1 computed from broadcast ephemeris;Acceleration of QZS-1 computed from broadcast ephemeris;• Perturbation only: Centripetal acceleration term is removed.Perturbation only: Centripetal acceleration term is removed.


2011-08-182011-08-1800:00 to 24:00 GPST00:00 to 24:00 GPST





SSLIDELIDE 2323Proposed Message (MT58)Proposed Message (MT58)

Item Bits Range Resolution Contents

t0,Q 8 0-10740 s 60 s Epoch time/IODN

URA 4 0-15 1 Accuracy indicator

x 26 42950 km 1.28 m Position X in ECEF

y 26 42950 km 1.28 m Position Y in ECEF

z 26 42950 km 1.28 m Position Z in ECEF

vx 24 4.194 km/s 0.5 mm/s Velocity X in ECEF

vy 24 4.194 km/s 0.5 mm/s Velocity Y in ECEF

vz 24 4.194 km/s 0.5 mm/s Velocity Z in ECEF

5 32 m/s2 2 m/s2 Acceleration X in ECEF (only perturbation)

5 32 m/s2 2 m/s2 Acceleration Y in ECEF (only perturbation)

5 32 m/s2 2 m/s2 Acceleration Z in ECEF (only perturbation)

aGf0 22 1.953 ms 2-30 s Clock correction (const)

aGf1 13 3.725 ns/s 2-40 s/s Clock correction (1st order)

Total 212 Stored in 1 msg (1s)

xx

yy

zz

....

....

....


SSLIDELIDE 2424Generation of EphemerisGeneration of Ephemeris

• Option A: Generation independent of other systems:Option A: Generation independent of other systems:– Need realtime monitor station network:Need realtime monitor station network:

Monitor stations also necessary for generation of wide-area differential corrections;Monitor stations also necessary for generation of wide-area differential corrections; JAXA’s monitor network covering Japan and Southeast Asia Region is available for eJAXA’s monitor network covering Japan and Southeast Asia Region is available for e

xperimental purpose.xperimental purpose.

– Need some orbit determination software;Need some orbit determination software;– Independent of other systems.Independent of other systems.

However, observations from monitor network are provided by JAXA MCS.However, observations from monitor network are provided by JAXA MCS.

• Option B: Reconstruction from MCS products:Option B: Reconstruction from MCS products:– L1-SAIF is broadcast from QZS-1 SV.L1-SAIF is broadcast from QZS-1 SV.

QZS-1 itself broadcasts ephemeris information on L1C/A signal;QZS-1 itself broadcasts ephemeris information on L1C/A signal;

– Ephemeris information can be generated based on L1C/A ephemeris;Ephemeris information can be generated based on L1C/A ephemeris; Reconstruction from Keplerian representation in L1C/A legacy Nav message into ECReconstruction from Keplerian representation in L1C/A legacy Nav message into EC

EF PVA representation for MT58;EF PVA representation for MT58; L1C/A and L1-SAIF are broadcast from different antennas; Antenna offset may be caL1C/A and L1-SAIF are broadcast from different antennas; Antenna offset may be ca

ncelled by differential corrections.ncelled by differential corrections.

– Users still do not need to receive any signals other than L1-SAIF.Users still do not need to receive any signals other than L1-SAIF.

We employWe employthis optionthis option


SSLIDELIDE 2525Ephemeris ReconstructionEphemeris Reconstruction

DecodeDecodeephemerisephemeris

ComputeComputePVAPVA

FormatFormatinto MT58into MT58

QZS-L1C

/A (P

RN 193

)

QZS-L1C

/A (P

RN 193

)

Ephem

eris

in Le

gacy

Nav

Ephem

eris

in Le

gacy

Nav

L1-SAIF (PRN 183)

L1-SAIF (PRN 183)

Ephemeris in MT58

Ephemeris in MT58

L1-SAIF Master Station at ENRIL1-SAIF Master Station at ENRI

JAXA MCSJAXA MCSQ

ZS

-L1C

/AQ

ZS

-L1C

/A Uplink

Uplink

Ephemeris ReconstructionEphemeris ReconstructionL1-C/A UsersL1-C/A Users

L1-SAIF UsersL1-SAIF Users

QZS-1QZS-1


SSLIDELIDE 2626

QZS-1QZS-1Reconstructed fromReconstructed frombroadcast Nav Msgbroadcast Nav Msgon L1C/A PRN 193on L1C/A PRN 193

2011-08-182011-08-1800:00 to 24:00 GPST00:00 to 24:00 GPST


Assumed user location:Assumed user location: @ENRI, Tokyo@ENRI, Tokyo

SV Position Error for PVA SV Position Error for PVA

• Integration error in user receiver with regard to time after broadcast of PVA;Integration error in user receiver with regard to time after broadcast of PVA;• LOS component including satellite clock offset;LOS component including satellite clock offset;• SV PVA is computed from broadcast ephemeris on QZSS L1C/A.SV PVA is computed from broadcast ephemeris on QZSS L1C/A.

Quantization of correctionsQuantization of corrections


SSLIDELIDE 2727SV Position Error for MT58SV Position Error for MT58

• PVA is formatted into proposed MT58 format and integrated;PVA is formatted into proposed MT58 format and integrated;• Initial position error is dominant component because of its resolution of Initial position error is dominant component because of its resolution of

1.28m; Need some correction.1.28m; Need some correction.


2011-08-182011-08-1800:00 to 24:00 GPST00:00 to 24:00 GPST




SSLIDELIDE 2828Correction by LTC MessageCorrection by LTC Message

MeasuredMeasuredPseudorangePseudorange

CorrectedCorrectedPseudorangePseudorange

OrbitOrbitClockClock

MeasuredMeasuredPseudorangePseudorange

CorrectedCorrectedPseudorangePseudorange

OrbitOrbitClockClock

ClockClockCorr.Corr.

ClockClockCorr.Corr.

Clock & Orbit Corr.Clock & Orbit Corr.

SBAS GEO SBAS GEO

QZSS L1-SAIFQZSS L1-SAIF

MT2-5MT2-5Fast CorrectionFast Correction

(FC)(FC)

MT2-5MT2-5Fast CorrectionFast Correction

(FC)(FC)

MT9MT9GEO EphemerisGEO Ephemeris

MT58MT58QZS EphemerisQZS Ephemeris

MT24/25MT24/25Long-TermLong-Term

Correction (LTC)Correction (LTC)

(0.125m)(0.125m) (0.125m)(0.125m)

(1.28m)(1.28m) (0.125m)(0.125m)

(0.125m)(0.125m)

• Apply MT24/25 LTC orbit and cloApply MT24/25 LTC orbit and clock correction like GPS SVs;ck correction like GPS SVs;

• LTC has 0.125m resolution.LTC has 0.125m resolution.

PRN 183PRN 183

PRN 120-138PRN 120-138

ResolutionResolution


SSLIDELIDE 2929Applying LTC CorrectionApplying LTC Correction

• Assumed that initial position error is corrected by LTC (long-term Assumed that initial position error is corrected by LTC (long-term correction) in MT24/25 messages;correction) in MT24/25 messages;

• Range error is within 0.3m for 300s integration. Range error is within 0.3m for 300s integration. Note that ephemeris message of SBAS has timeout interval of 240-360s.Note that ephemeris message of SBAS has timeout interval of 240-360s.


2011-08-182011-08-1800:00 to 24:00 GPST00:00 to 24:00 GPST




SSLIDELIDE 3030ConclusionConclusion

• ENRI has been developing L1-SAIF signalENRI has been developing L1-SAIF signal::– Signal design: GPS/SBAS-like L1 C/A code (PRN 183);Signal design: GPS/SBAS-like L1 C/A code (PRN 183);

– Planned as an augmentation to mobile users;Planned as an augmentation to mobile users;

– Implemented L1-SAIF Master Station (L1SMS) which generates augmentation messImplemented L1-SAIF Master Station (L1SMS) which generates augmentation message stream in realtime and transmit it to QZSS MCS.age stream in realtime and transmit it to QZSS MCS.

• QZSS ephemeris messageQZSS ephemeris message::– Need to broadcast ephemeris information to make ranging function available;Need to broadcast ephemeris information to make ranging function available;

– For L1-SAIF signal, MT 58 is designed to broadcast ephemeris information;For L1-SAIF signal, MT 58 is designed to broadcast ephemeris information;

– MT 58 provides SV position, velocity, and acceleration in ECEF;MT 58 provides SV position, velocity, and acceleration in ECEF;

– Integration error is within 0.3m when combined with LTC correction.Integration error is within 0.3m when combined with LTC correction.

• Ongoing workOngoing work::– Upgrade L1SMS to generate corrections for L1-SAIF signal itself;Upgrade L1SMS to generate corrections for L1-SAIF signal itself;

– User side consideration of combined use of QZSS and MSAS.User side consideration of combined use of QZSS and MSAS.

Documents

T. Sakai, H. Yamada, S. Fukushima, and K. Ito Electronic Navigation Research Institute, Japan T. Sakai, H. Yamada, S. Fukushima, and K. Ito Electronic